xhci 1.0: Set transfer burst last packet count field.

The xHCI 1.0 specification defines a new isochronous TRB field, called
transfer burst last packet count (TBLPC).  This field defines the number
of packets in the last "burst" of packets in a TD.  Only SuperSpeed
endpoints can handle more than one burst, so this is set to the number for
packets in a TD for all non-SuperSpeed devices (minus one, since the field
is zero based).

This patch should have no effect on host controllers that don't advertise
the xHCI 1.0 (0x100) version number in their hci_version field.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

1 files changed, 40 insertions, 1 deletions

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index cc5963263a6..396f8d2a2e8 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -3144,6 +3144,42 @@ static unsigned int xhci_get_burst_count(struct xhci_hcd *xhci,
 	return roundup(total_packet_count, max_burst + 1) - 1;
 }
 
+/*
+ * Returns the number of packets in the last "burst" of packets.  This field is
+ * valid for all speeds of devices.  USB 2.0 devices can only do one "burst", so
+ * the last burst packet count is equal to the total number of packets in the
+ * TD.  SuperSpeed endpoints can have up to 3 bursts.  All but the last burst
+ * must contain (bMaxBurst + 1) number of packets, but the last burst can
+ * contain 1 to (bMaxBurst + 1) packets.
+ */
+static unsigned int xhci_get_last_burst_packet_count(struct xhci_hcd *xhci,
+		struct usb_device *udev,
+		struct urb *urb, unsigned int total_packet_count)
+{
+	unsigned int max_burst;
+	unsigned int residue;
+
+	if (xhci->hci_version < 0x100)
+		return 0;
+
+	switch (udev->speed) {
+	case USB_SPEED_SUPER:
+		/* bMaxBurst is zero based: 0 means 1 packet per burst */
+		max_burst = urb->ep->ss_ep_comp.bMaxBurst;
+		residue = total_packet_count % (max_burst + 1);
+		/* If residue is zero, the last burst contains (max_burst + 1)
+		 * number of packets, but the TLBPC field is zero-based.
+		 */
+		if (residue == 0)
+			return max_burst;
+		return residue - 1;
+	default:
+		if (total_packet_count == 0)
+			return 0;
+		return total_packet_count - 1;
+	}
+}
+
 /* This is for isoc transfer */
 static int xhci_queue_isoc_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 		struct urb *urb, int slot_id, unsigned int ep_index)
@@ -3186,6 +3222,7 @@ static int xhci_queue_isoc_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 	for (i = 0; i < num_tds; i++) {
 		unsigned int total_packet_count;
 		unsigned int burst_count;
+		unsigned int residue;
 
 		first_trb = true;
 		running_total = 0;
@@ -3197,6 +3234,8 @@ static int xhci_queue_isoc_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 				le16_to_cpu(urb->ep->desc.wMaxPacketSize));
 		burst_count = xhci_get_burst_count(xhci, urb->dev, urb,
 				total_packet_count);
+		residue = xhci_get_last_burst_packet_count(xhci,
+				urb->dev, urb, total_packet_count);
 
 		trbs_per_td = count_isoc_trbs_needed(xhci, urb, i);
 
@@ -3210,7 +3249,7 @@ static int xhci_queue_isoc_tx(struct xhci_hcd *xhci, gfp_t mem_flags,
 
 		for (j = 0; j < trbs_per_td; j++) {
 			u32 remainder = 0;
-			field = TRB_TBC(burst_count);
+			field = TRB_TBC(burst_count) | TRB_TLBPC(residue);
 
 			if (first_trb) {
 				/* Queue the isoc TRB */